Editing IBM PC compatible (section)

==Origins==
[[File:IBM PC 5150.jpg|thumb|right|250px|The original [[IBM Personal Computer|IBM PC]] (Model 5150) motivated the production of clones during the early 1980s.]]

IBM decided in 1980 to market a low-cost single-user computer as quickly as possible. On August 12, 1981, the first [[IBM Personal Computer|IBM PC]] went on sale. There were three [[operating system]]s (OS) available for it. The least expensive and most popular was [[IBM PC DOS|PC DOS]] made by [[Microsoft]]. In a crucial concession, IBM's agreement allowed Microsoft to sell its own version, [[MS-DOS]], for non-IBM computers. The only component of the original PC architecture exclusive to IBM was the [[BIOS]] (Basic Input/Output System).

IBM at first asked developers to avoid writing software that addressed the computer's hardware directly and to instead make standard calls to BIOS functions that carried out hardware-dependent operations.<ref name="norton19850205">{{cite news |url=https://books.google.com/books?id=BGNWNTJnuRcC&pg=PA101 | title=Software for Once and All | work=PC Magazine | date=February 5, 1985 | access-date=October 28, 2013 | author=Norton, Peter | pages=103}}</ref> This software would run on any machine using MS-DOS or PC DOS. Software that directly addressed the hardware instead of making standard calls was faster, however; this was particularly relevant to games. Software addressing IBM PC hardware in this way would not run on MS-DOS machines with different hardware (for example, the [[PC-98]]). The IBM PC was sold in high enough volumes to justify writing software specifically for it, and this encouraged other manufacturers to produce machines that could use the same programs, [[expansion card]]s, and peripherals as the PC. The [[x86]] computer marketplace rapidly excluded all machines which were not hardware-compatible or software-compatible with the PC. The [[Conventional memory#640 KB barrier|640&nbsp;KB barrier]] on "conventional" system memory available to MS-DOS is a legacy of that period; other non-clone machines, while subject to a limit, could exceed 640&nbsp;KB.

Rumors of "lookalike," compatible computers, created without IBM's approval, began almost immediately after the IBM PC's release.<ref name="libes198112">{{cite news | url=https://archive.org/stream/byte-magazine-1981-12/1981_12_BYTE_06-12_Computer_Games#page/n315/mode/2up | title=Bytelines | work=BYTE | date=December 1981 | access-date=January 29, 2015 | author=Libes, Sol | pages=314–318}}</ref><ref name="pclookalikes19820203">{{cite news |url=https://books.google.com/books?id=w_OhaFDePS4C&pg=PA5 | title=Lookalikes From Home & Abroad | work=PC Magazine | date=February–March 1982 | access-date=October 20, 2013 | pages=5}}</ref> ''InfoWorld'' wrote on the first anniversary of the IBM PC that<ref name="zussman19820823">{{cite news | url=https://books.google.com/books?id=VDAEAAAAMBAJ&pg=PA29 | title=Let's keep those systems open | work=InfoWorld | date=August 23, 1982 | access-date=January 29, 2015 | author=Zussman, John Unger | page=29}}</ref>

{{quote|The dark side of an open system is its imitators. If the specs are clear enough for you to design peripherals, they are clear enough for you to design imitations. Apple ... has patents on two important components of its systems ... IBM, which reportedly has no special patents on the PC, is even more vulnerable. Numerous PC-compatible machines—the grapevine says ''60'' or more—have begun to appear in the marketplace.}}

By June 1983 ''[[PC Magazine]]'' defined "PC 'clone{{'"}} as "a computer [that can] accommodate the user who takes a disk home from an IBM PC, walks across the room, and plugs it into the 'foreign' machine".<ref name="sandler198306">{{cite news |url=https://books.google.com/books?id=14Kfbrc6cbAC&q=pc%20mag%20june%201983&pg=PA31 | title=Getting To Know You | work=PC Magazine | date=June 1983 | access-date=October 21, 2013 | author=Sandler, Corey | pages=31}}</ref> Demand for the PC by then was so strong that dealers received 60% or less of the inventory they wanted,<ref name="hayes19831024">{{Cite news |url=https://www.nytimes.com/1983/10/24/business/eagle-computer-stays-in-the-race.html |title=Eagle Computer Stays in the Race |last=Hayes |first=Thomas C. |date=1983-10-24 |work=The New York Times |access-date=10 January 2015 |page=D4 |url-access=limited}}</ref> and many customers purchased clones instead.<ref name="barmash19830610">{{Cite news |url=https://www.nytimes.com/1983/06/10/business/corporate-triumph-then-death-in-a-ferrari.html |title=Corporate Triumph, Then Death in a Ferrari |last=Barmash |first=Isadore |date=June 10, 1983 |work=The New York Times |access-date=June 19, 2019 |page=A1 |language=en-US |issn=0362-4331}}</ref>{{r|mace19840109_16}}<ref name="pc19840124">{{cite news |url=https://books.google.com/books?id=kSzKzjWHeVEC&pg=PA39 | title=PC-Compatible Portables | work=PC Magazine | date=January 24, 1984 | access-date=October 23, 2013 |author1=Cook, Karen |author2=Langdell, James | pages=39}}</ref> [[Columbia Data Products]] produced the first computer more or less compatible with the IBM PC standard during June 1982, soon followed by [[Eagle Computer]]. [[Compaq]] announced its first product, an IBM PC compatible in November 1982, the [[Compaq Portable]]. The Compaq was the first sewing machine-sized [[portable computer]] that was essentially 100% PC-compatible. The court decision in ''[[Apple Computer, Inc. v. Franklin Computer Corp.|Apple v. Franklin]]'', was that BIOS code was protected by copyright law, but it could [[reverse engineering|reverse-engineer]] the IBM BIOS and then write its own BIOS using [[clean room design]]. Note this was over a year after Compaq released the Portable. The money and research put into reverse-engineering the BIOS was a calculated risk.